In order to transmit electrical current to or from a flat blade contact, it is standard to provide an electrical socket with a plurality of parallel spring contacts forming an elongated slot into which the blade can fit. Thus U.S. Pat. No. 6,210,240 of Comerci describes such a socket formed basically of a single piece of springy sheet metal bent to form two sets of contact fingers that in turn form the elongated blade-receiving slot. The fingers thus bear on opposite faces of a blade inserted into the socket so as to create a plurality of contact regions capable of transmitting considerable current, as for instance in a motor-vehicle fuse block. Medium currents of 16 amp and more and high currents of 50 amp and more can move through such a socket assembly.
The individual fingers of the socket assembly are deformed in the plane of the sheet metal forming them so they are quite springy. All of the contact fingers are therefore identical.
The problem with this construction is that the sheet metal must be specially stamped for each socket size. A socket for transmitting heavy current must have more such contact fingers than one transmitting less current. Thus the manufacturer must dispose of as many dies as there are socket sizes, greatly adding to production costs.
Another disadvantage of this type of socket is that it is necessary to provide as many fingers as possible in each socket, as they bear with relatively modest transverse force on the blade fitted to the socket. This has, once again, the disadvantage that each socket must be specifically designed for the load it is intended to carry.